1. Field of the Invention
This invention relates generally to refrigerator air circulation systems and, more particularly, to an improved air circulation system for controlling the position of a baffle in a dual zone circulation system.
2. Description of Background Art
Conventional dual compartment refrigerators of the forced air circulation type utilize a single evaporator and an evaporator fan for cooling a freezer compartment thereof. The freezer compartment is coupled by a plurality of air passages through a divider wall to a fresh food compartment. An air baffle has been located within the fresh food compartment air inlet passage. The baffle is operable to control the passage of refrigerated air into the fresh food compartment. Such an arrangement is shown in Janke, U.S. Pat. No. 4,682,474, assigned to the assignee of the present invention.
With such a conventional refrigerator, if the refrigeration unit is operating, then the evaporator fan forces the air flow across the evaporator coils and out the top of the freezer into a scoop which directs air into the fresh food compartment, past the baffle. The fan flow overcomes natural conductive flow caused by air density differences. Resultantly, with the fan on, air enters at the top, circulating within the fresh food compartment, and returns out the bottom through an air outlet passage back to the freezer compartment.
During a conventional automatic defrost cycle, moisture can accumulate on the baffle. Once the defrost cycle is complete, the subsequent unit cycle time is of greater length since the cabinet must overcome heat produced by the defrost heater. The colder air from the evaporator coils can cause moisture on the baffle to freeze. The resulting ice prevents free movement of the baffle resulting in over-cooling of the fresh food compartment.
When the evaporator fan is off, air flow is controlled by a natural convection. The colder freezer air flows from the freezer bottom in a reverse direction through the compartment air outlet into the bottom of the fresh food compartment. With high ambient temperatures, where unit off time is short, such periods of uncontrolled back flow are short in duration so that performance is not hampered. However, with lower ambient temperatures, the unit off time tends to be greater in duration resulting in periods of uncontrolled back flow being longer. These long periods of back flow may result in the bottom portion of the fresh food compartment being overcooled causing freezing of articles therein.
Janke et al co-pending application, owned by the assignee of the present invention, describes a refrigeration apparatus which is provided with a controllable baffle at the fresh food compartment air outlet to minimize uncontrolled back flow. Also, a plurality of air inlets are included, including an air inlet located at the bottom section of the fresh food compartment, to provide for direct cooling at preselected zones of the refrigerator. Temperature control is provided by the position of the single air outlet baffle. Since a single outlet baffle is used, temperature is generally uniform throughout the fresh food compartment.
The present invention improves on the above refrigerator air circulation systems in a novel and simple manner.